WASHINGTON—A Pew Forum poll on Americans and their religious affiliation finds Catholics have one of the highest retention rates, 68 percent, among Christian churches when it comes to carrying the Catholic faith into adulthood.

It also found that a determining factor in whether or not one remains Catholic as an adult is whether or not the individual attended Mass as a child and teenager.

The study also found that the key reason people leave their church, Protestant or Catholic, is that “they just gradually drifted away from the faith.”

The study, “Faith in Flux: Changes in the Religious Affiliation in the U.S.,” was made public by the Pew Forum on Religion and Public Life, April 27.

Pew also found that only 2-3 percent of those polled cited sexual abuse of children as a reason for leaving when asked in an open-ended question why they left. When people were asked to choose why they left from a list of possible reasons, the number jumped from 21 percent for Catholics who became Protestant and 27 percent for former Catholics who are now unaffiliated with any church. Other reasons for leaving the church, such as disagreement on doctrinal matters, figured much higher.

“The report highlights the importance of Mass attendance among children and teenagers,” said Archbishop Donald W. Wuerl of Washington, past chairman of the bishops’ Committee on Catechesis and next chairman of the Committee on Doctrine. “Adolescence is a critical time in religious development and, as the poll shows, what happens in the teen years has a long-lasting affect. We have to help young people and their parents appreciate the importance of going to weekly Mass so teenagers know Jesus is there for them now and always.“

Archbishop Wuerl said the poll showed the resilience of the Catholic faith, even in the face of something as horrific as the sexual abuse crisis.

“Catholics can separate the sins and human failings of individuals from the substance of the faith,” he said. “Sexual abuse of a child is a terrible sin and crime,” he said, “but most Catholics people, because of good personal experience with their priests in their parishes, recognize sex abuse by clergy as the aberration it is. They also look to the church’s 2,000-year history, which has seen the faith flourish despite some painful times.”